Question

two blocks of mass 4kg and 2kg are attached by an inextensible light string.Both the blocks are pulled vertically upward by a force F=120N. Then the acceleration of the blocks is?

Answer 1

F = 120 N
total mas = 4+2=6
F=ma
a=F/m
= 120/6
= 20 m/s2

Answer 2

Explanation:

Let a be the acceleration of the blocks and T the tension in the string as shown in the figure.

Taking the two blocks and the string as the system shown in figure

Using we get ΣFy=m×ay,

F−4g−2g=(4+2)a

or 120−40−20=6a

or 60=6a

∴a=10m/s